Deformation-softening behaviors of high-strength and high-toughness steels used for rock bolts

In deep ground engineering,the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity.However,the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature.In this study,taking Muzhailing highway tunnel as the background,physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity(TWIP)steel used for rock bolt.The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling.The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface.The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate.There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning.The high pretension(>600 MPa or 224 k N)can help bolt rod steel resist deformation-softening behavior,especially at low loading rate(<10~(-1)MPa/s or 10~(-2)kN/s).The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario.The results provide the theoretical basis and technical support for practical applications.

Numerical Model Research on Rotational Performance of Beam-Column High-Strength Bolt Extension End-Plate Connection Node

The high-strength bolted end plate connection is widely used in the construction industry with its green environmental protection and excellent seismic performance. The joints of the joints are semi-rigid, the force performance is extremely complicated, and the experimental research cost is relatively high, and the cycle is very long. Therefore, the establishment of an efficient numerical model is of great significance for evaluating the force performance of high-strength bolt end plates. In this paper, the influence of different material models on the rotation performance of the joint is studied by numerical simulation, and the bending moment-rotation curve is obtained. The numerical simulation and the experimental results are in good agreement, so as to provide a reference for the design and application of this kind of joint.

超大断面扁平结构隧道施工参数优化研究

基于某超大断面扁平结构隧道的上下台阶法施工段,采用数值模拟方法研究在该工程地质条件下台阶长度和锚杆纵距2种施工参数改变带来的影响。利用数值模型对不同台阶长度(分别为30,40,50,60 m)和不同锚杆纵距(分别为1.0,1.5,2.0 m)情况进行研究,对隧洞周边岩体中塑性区、围岩应力和围岩变形情况的分布规律进行分析,结合数值结果和现场监测数据验证了施工现场采用台阶长度为50 m和锚杆纵距为1 m的施工参数较合理。该研究成果可为超大断面扁平结构隧道的开挖和支护施工参数的合理选取提供参考。

超厚大体积混凝土底板钢结构柱脚锚栓施工技术

以深圳市深圳湾超级总部基地地标建筑OPPO国际总部项目为例,阐述了主塔楼钢结构柱脚锚栓的施工实践经验,分析了超厚大体积混凝土底板钢结构柱脚锚栓快速有效安装的一种创新思路及实施效果。

Influence of anchorage length and pretension on the working resistance of rock bolt based on its tensile characteristics

In coal mining roadway support design,the working resistance of the rock bolt is the key factor affecting its maximum support load.Effective improvement of the working resistance is of great significance to roadway support.Based on the rock bolt’s tensile characteristics and the mining roadway surrounding rock deformation,a mechanical model for calculating the working resistance of the rock bolt was established and solved.Taking the mining roadway of the 17102(3)working face at the Panji No.3 Coal Mine of China as a research site,with a quadrilateral section roadway,the influence of pretension and anchorage length on the working resistance of high-strength and ordinary rock bolts in the middle and corner of the roadway is studied.The results show that when the bolt is in the elastic stage,increasing the pretension and anchorage length can effectively improve the working resistance.When the bolt is in the yield and strain-strengthening stages,increasing the pretension and anchorage length cannot effectively improve the working resistance.The influence of pretension and anchorage length on the ordinary and high-strength bolts is similar.The ordinary bolt’s working resistance is approximately 25 kN less than that of the high-strength bolt.When pretension and anchorage length are considered separately,the best pretensions of the high-strength bolt in the middle of the roadway side and the roadway corner are 41.55 and 104.26 kN,respectively,and the best anchorage lengths are 1.54 and 2.12 m,respectively.The best anchorage length of the ordinary bolt is the same as that of the high-strength bolt,and the best pretension for the ordinary bolt in the middle of the roadway side and at the roadway corner is 33.51 and 85.12 kN,respectively.The research results can provide a theoretical basis for supporting the design of quadrilateral mining roadways.

Study on Fracture Delay of High-Strength Bolts in Road Bridge Maintenance

In the maintenance work of highway and bridge engineering structures,the fracture delay of high-strength bolts is a content that needs to be focused on and researched.Based on this,the paper analyzes the fracture delay of high-strength bolts in highway bridge maintenance,including an overview of the fundamental research on fracture delay and related specific studies.It is hoped that this study can provide scientific reference for the reasonable maintenance of high-strength bolts,so as to ensure the overall maintenance effect of highway bridge projects.

基于特征迁移的螺栓图像超分辨率处理方法

针对输电线路巡检采集的螺栓图像存在模糊、分辨率低等问题,本文根据螺栓之间相似度较高的特点,提出了一种基于特征迁移的螺栓图像超分辨率处理方法。本文首次将特征迁移引入螺栓图像超分中,先对比低分辨率图像与清晰参考图像的特征区域,将图像之间相似度高的区域进行特征迁移,并根据迁移特征的相似度调整迁移特征的比例,然后在感知损失函数中加入迁移特征相似度的约束,保证迁移特征的准确性。不同超分模型的螺栓图像超分实验结果表明,本方法的螺栓超分图像更清晰,峰值信噪比、结构相似性指标更优;此外,超分前后螺栓图像的缺陷识别实验对比结果表明,超分后螺栓的缺陷识别准确率提升了3.61%,实验结果验证了本文方法的有效性。

超高强度螺栓材料高温力学性能实验设计

为研究高温环境中高强螺栓的变形与断裂过程及力学性能的变化规律,在20~750℃(间隔50或者100℃)环境下对10.9级高强度螺栓(HB)和14.9级超高强度螺栓(SHTB)的力学性能进行了测试:利用振动法测试了2种螺栓的高温弹性模量;用高温拉伸试验机测试了2种螺栓在不同温度下的屈服强度、抗拉强度、峰值应变、断后伸长率、断面收缩率以及断裂应变,并建立了2种螺栓7个高温力学性能的数学模型。结果表明:在相同温度(20≤T≤750℃)下,2种螺栓的破坏形态基本相同,但14.9级SHTB的屈服强度和抗拉强度及相应的折减系数均高于10.9级HB;T>400℃时,二者峰值应变显著减小;T=750℃时,二者的抗拉强度值均不足常温时的10%;T≤600℃时,14.9级SHTB断后伸长率、断面收缩率均低于10.9级HB,但其折减系数相当甚至更高。

Hydrogen-induced delayed fracture of Cu-containing high-strength bolt steel

The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole solution.It is shown that the addition of Cu is beneficial to enhance the HIDF resistance by~13%.The observation of the fracture surface revealed that the area fraction of brittle crack initiation zone decreased remarkably for the Cu-added steel.Both the corrosion pit depth and the corrosion rate of the Cu-added steel in the Walpole solution are notably decreased,which is primarily because of the formation of a Cu-rich protective compact rust layer and slightly higher corrosion potential.As a result,the absorbed hydrogen content in that solution was also decreased by~21%.It is concluded that the improvement in the HIDF resistance of the tested steel is primarily due to the increase in corrosion resistance and resultant decrease in the absorbed diffusible hydrogen content in the acidic condition.

巷道与超大孔径射流孔双重开挖下煤体扰动规律

为了揭示巷道与超大孔径射流孔双重开挖对煤体的扰动规律,提高现场作业效率,采用ABAQUS数值模拟软件进行了考虑巷道开挖及支护、钻孔开挖及地应力平衡、煤层倾角及地层属性的模拟。确定了双重开挖下的钻孔周围三维扰动区域分布图,揭示了钻孔周围煤体扰动区域分布特征,并发现竖直方向扰动范围较大、扰动程度较高,巷道两侧和顶板锚杆的支撑区域、巷道与锚杆之间的区域是主要双重开挖扰动叠加的区域。同时,采用现场监测数据佐证了模拟结果的正确性。最终,为制定高效的煤与瓦斯共采作业方案提供了理论支撑。

An ultra-thin bolt tension sensor and online monitoring system:For application in hydropower plant unit

The condition of bolted connections significantly affects the structural safety.However,conventional bolt tension sensors fail to provide precise measurements due to their bulky size or inadequate stability.This study employs the piezoresistive effect of crystalline silicon material to fabricate an ultrathin sensor.The sensor exhibits a linear relationship between pressure and voltage,an exceptional stability at varying temperatures,and a superior resistance to corrosion,making it adaptable and user-friendly for applications of high-strength bolt tension monitoring.A monitoring system,incorporating the proposed sensor,has also been developed.This system provides real-time display of bolt tension and enables the assessment of sensor and structural conditions,including bolt loosening or component failure.The efficacy of the proposed sensor and monitoring system was validated through a project carried out at the Xiluodu Hydropower Plant.According to the results,the sensor and online monitoring system effectively gauged and proficiently conveyed and stored bolt tension data.In addition,correlations were created between bolt tensions and essential unit parameters,such as water head,active power,and pressures at vital points,facilitating anomaly detection and early warning.

大吨位锚杆静压桩施工要点

锚杆静压桩是高层建筑基础加固工程中一种常用的有效方式,随着施工能力的提升,锚杆静压桩的压桩力可达到500 t以上,为了保证施工质量,必须采取严格的管理措施。以广东地区某189 m超高层建筑为例,介绍大吨位锚杆静压桩在超高层建筑物基础加固中的应用,通过对锚杆质量、压桩垂直度和动阻力、桩端注浆等施工工艺进行控制,取得了良好的加固效果,单桩承载力特征值达到了3 500 kN,最终建筑物沉降仅32 mm左右,为相似工程提供了一定的参考。

日本钢桥高强度螺栓病害处治与新型螺栓研究

高强度螺栓连接是日本钢结构桥梁常用的连接形式,对日本钢桥用高强度螺栓病害处治措施及新型螺栓研发应用进行介绍。结合日本2座钢结构桥梁工程实例,对高强度螺栓断裂、掉落和索夹螺栓轴力减小等病害原因进行分析,为确保桥梁安全运营,对全部螺栓进行了补拧与更换。针对螺栓生锈、腐蚀,开发了新型防腐涂层材料SZ工法,该工法选择锌作为高强度螺栓表面的牺牲防腐保护膜,试验及应用结果表明防腐效果较好。延迟断裂是高强度螺栓常见病害,研发了耐延迟断裂优质钢及螺栓,改善耐氢脆化特性,并在此基础上研发了超高强度高可靠性(FS)螺栓,室外暴露试验证明,FS螺栓具有优越的耐延迟破坏性能。针对钢桥面板连接接头处凹凸不平现象,开发了高强度沉头螺栓,并在实际工程中应用。

锚杆支护超长煤巷顶板稳定性动态分类研究

针对神东矿区煤巷长度超长、巷道断面大、顶板岩层结构变化复杂及锚杆支护率高等实际情况和锚杆(索)支护的工程特性,依据围岩稳定性分类指标的科学性、实用性及可定量化的选取原则,在深入分析神东矿区锚杆支护煤巷顶板稳定性主要影响因素的基础上,研究确定了单层厚岩层离顶板表面距离L、单层厚岩层抗压强度σc、单层厚岩层厚度D、巷道跨度B、巷道埋深H、采动影响指标N六个分类指标作为神东矿区锚杆支护超长煤巷顶板稳定性分区动态分类指标,并构建了神东矿区锚杆支护超长煤巷顶板稳定性分区动态分类的BP神经网络预测模型,经检验该神经网络模型的识别准确率大于95%,利用该网络模型进行动态分类的结果与现场实际高度吻合。

大伙房输水工程特长隧洞TBM选型及支护系统优化研究

研究目的:大伙房输水工程特长隧洞主洞长85.32 km,开挖洞径8.03 m,属于深埋特长隧洞。由于隧洞施工采用以TBM为主、钻爆法为辅的联合施工方式。隧洞穿越区域水文地质条件复杂,通过对TBM合理选型和支护系统优化,来解决隧洞开挖过程中面临的围岩稳定性、隧洞涌水、石英砂岩的掘进效率及岩爆等三大关键技术难题。研究结论:通过对大量文献资料和工程实例的研究,对大伙房特长隧洞所穿越区域的主要工程地质问题进行分析,并结合国内外已有的TBM施工经验,特长隧洞决定选用敞开式TBM,锚喷支护+模筑混凝土复合衬砌结构支护系统代替管片衬砌结构。对大伙房输水工程特长隧洞的建成发挥了重要的保证作用,也为今后类似工程提供参考和借鉴。

深井松散煤巷超高强预应力组合锚杆支护技术

深井松散煤巷支护一直是制约矿井安全生产的难题,常规的锚杆支护方式及支护强度已很难适应其变形特征。文中以丁集煤矿1262(1)巷道为例,在新型锚杆强化支护体系的应用研究中,采用了超高强预应力组合锚杆支护技术,通过加大支护强度及采取各种补强措施,进一步优化围岩应力场,充分调动围岩自身承载能力,有效控制了巷道围岩变形,实现了巷道长期稳定,满足了矿井的安全高效生产,并为该类煤层巷道推行锚杆支护技术提供了参考和借鉴。

超高压压缩机气缸螺栓疲劳寿命评估

超高压压缩机气缸螺栓在交变载荷作用下,会产生疲劳失效破坏。文中介绍了二次机气缸螺栓疲劳寿命的分析方法,利用裂纹扩展速率与螺栓的临界裂纹尺寸对含缺陷的螺栓疲劳寿命进行了计算,为设备的诊断维护提供了合理的依据。

大采高超大断面切眼长锚杆锚索组合支护技术

为了解决大采高工作面超大断面切眼的支护问题,在赵固二矿1105切眼导硐进行了顶板岩层结构精细探测和岩层移动规律研究,结果表明赵固二矿1105切眼顶板表面至深部呈现裂隙密集区、裂隙渐疏区、裂隙稀少区等特征,3.5m以上裂隙发育较少,顶板4～6m范围内为稳定岩层,据此提出了长锚杆锚索组合支护技术,并采用理论计算、计算机数值模拟方法对支护参数进行了优化设计。该方案在赵固二矿1105超大断面切眼进行了现场应用,监测结果表明该方案能够有效控制巷道围岩,长锚杆支护效果良好。

极早熟耐抽薹大白菜新品种‘陕春白1号’

‘陕春白 1号’大白菜是在原 95S17 1和 95S2 4配制的早熟组合‘96杂 3’的基础上 ,通过对双亲人工春化耐抽薹性筛选育成的春大白菜一代杂种。该品种属叠抱类型 ,结球速度快 ,保护地栽培从定植到收获 4 5～ 5 0d ,单球质量 1.5～ 2 .0kg ,结球极紧实 ,抗病毒病、霜霉病和软腐病 。

形状记忆合金在法兰密封连接中的应用

形状记忆合金的记忆效应和超弹性可以用来补偿法兰密封连接由于蠕变松弛所造成的密封压紧力下降,提高法兰密封连接的可靠性。本文概述了目前国外形状记忆合金在法兰密封连接中的应用研究现状,对Ti-Ni-Pd、Ti-Ni-Hf、Fe-Mn-Si、Cu-Al-Ni和Ni-Al-Mn等合金在法兰连接上的应用前景作了初步探讨。分析认为,将形状记忆合金用于法兰连接中,除了需要考虑法兰密封连接的结构设计外,还需要积累大量基础研究数据,深入研究其记忆效应和母相状态下的压缩回弹特性,从而在对密封压紧力的稳定性和可靠性进行综合考虑后,开发出适用的高性能法兰密封连接。